In solid-vapor sorption reaction systems, a gaseous reactant is alternately absorbed and desorbed on a solid sorbent in one or more reaction chambers in a sorber or reactor. Where multiple reactors are used the system can operate in substantially opposing phases, or half-cycles, with one reactor or bank of reactors desorbing the gaseous reactant from the solid sorbent while the other reactor or bank of reactors is absorbing the gaseous reactant on the solid sorbent.
Once the reactant is desorbed from the solid sorbent it can be directed to one or more condensers. After condensation, the condensate is then directed to one or more evaporators where it is vaporized back into a gas. During this process, heat may be rejected from the condenser and cooling may be recovered from the evaporator.
In other systems, the reactors are used instead of condensers and evaporators for recovering energy from the refrigerant. Desorption is carried out by heating the solid sorbent on which the gaseous reactant has been absorbed. Electric, steam, or gas-driven heaters are typically used for heating the solid sorbent. A heat transfer fluid can then be directed through a reactor heat exchanger to which the sorbent is thermally exposed. To initiate absorption, a solid sorbent, from which the gaseous reactant or refrigerant has been desorbed, is cooled to a suitable temperature whereby it draws the gaseous refrigerant from the evaporator. The reactors may also be provided with heat exchangers and piping for directing heat transfer fluid between the reactors so that heat released from an absorbing reactor is directed to a desorbing reactor to provide heating to carry out desorption. Such systems are described in, for example U.S. Pat. Nos. 5,079,928, 5,263,330, 5,477,706, 5,598,721, 5,628,205, and 6,477,856, all of which disclosures are incorporated herein by reference in their entirety.
During a reaction cycle, a first (absorbing) reactor is at a lower temperature than a second (desorbing) reactor. This means that the temperature of the solid sorbent and other components within the second reactor is higher than the temperature of the solid sorbent and all other components in the first reactor. At the end of a half-cycle, with a majority of gaseous reactant desorbed from the sorbent in the second reactor and a majority of gaseous reactant absorbed on the sorbent in the first reactor, the absorption/desorption phases are reversed.
At this half-point of the cycle, the second reactor is then cooled and the first reactor is heated. At least partial heating of the first reactor can be supplied by directing heat from the second reactor to the first reactor. This recuperation of energy from the second reactor can increase the overall energy efficiency of the system since less external heating is required to heat the first reactor.
The overall efficiency can also be increased by cooling the second reactor by transferring a portion of any condensed refrigerant to the heat exchange section of the second reactor. Such cooling may be assisted by utilizing vaporized heat transfer fluid or refrigerant for driving the liquid heat transfer fluid or refrigerant in the cooling loop, such as disclosed in U.S. Pat. No. 5,477,706.